Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can prov...Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.展开更多
Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature dis...Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.展开更多
Three-dimensional(3 D) hybrid of nanocarbons is a very promising way to the high-performance design of electrocatalysis materials.However,sp^(3)-like defect structure,a combination of high strength and conduction of g...Three-dimensional(3 D) hybrid of nanocarbons is a very promising way to the high-performance design of electrocatalysis materials.However,sp^(3)-like defect structure,a combination of high strength and conduction of graphene and carbon nanotubes(CNTs) is rarely reported.Herein,3 D neural-like hybrids of graphene(from reduced graphene oxide) and carbon nanotubes(CNTs) have been integrated via sp^(3)-like defect structure by a hydrothermal approach.The sp^(3)-like defect structure endows 3 D nanocarbon hybrids with an enhanced carrier transfer,high structural stability,and electrocatalytic durability.The neural-like structure is shown to demonstrate a cascade effect of charges and significant performances regarding bio-electrocatalysis and lithium-sulfur energy storage.The concept and mechanism of "sp^(3)-like defect structure" are proposed at an atomic/nanoscale to clarify the generation of rational structure as well as the cascade electron transfer.展开更多
As a mixed conductor,LaSr3Fe3O10-δ with triple layer perovskite intergrowth structure can be used as an oxygen separation membrane material and cathode material in solid oxide fuell cells.LaSr3Fe3O10-δ was synthesiz...As a mixed conductor,LaSr3Fe3O10-δ with triple layer perovskite intergrowth structure can be used as an oxygen separation membrane material and cathode material in solid oxide fuell cells.LaSr3Fe3O10-δ was synthesized via citrate acid route.Iodine titration method was used to determine the average valence of transition metal Fe and oxygen nonstoichiometry δ.Conductivities of LaSr3Fe3O10-δ were measured in the oxygen partial pressure range from 10-2×105 to 1×105 Pa,by Ac four probe method.Seebeck coefficient...展开更多
The dielectric properties of ceramics with composition of (Sr 1-x Bi x )TiO 3+x/2 (where x =0.05～0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr 1-x...The dielectric properties of ceramics with composition of (Sr 1-x Bi x )TiO 3+x/2 (where x =0.05～0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr 1-x Bi x )TiO 3+x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi 2O 3. The relative permittivity of the solid solutions is high, and the dissipation factor is low. The positron annihilation technique(PAT) was adopted to study the defect structure. An explanation of the dielectric properties of Bi-doped SrTiO 3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism.展开更多
A set of potential parameters for modeling zircon was obtained by atomistic simulation techniques and a reasonable structural model of zircon was established by fitting some important properties of zircon.Based on the...A set of potential parameters for modeling zircon was obtained by atomistic simulation techniques and a reasonable structural model of zircon was established by fitting some important properties of zircon.Based on the equilibrium configuration of zircon, authors calculated the formation energies of basic point defects and intrinsic disorders. The heats of solution of substituting Pu for Zr showed that there was an immiscible gap at the composition of (Pu75%-Zr25%, in mole fraction), which suggests that the amount of Pu substituting for Zr in zircon be≤50%.展开更多
Layered Ni-rich transition metal oxide is treated as the most promising alternative cathode due to their high-capacity and flexible composition.However,the severe lattice strain and slow Li-ion migration kinetics seve...Layered Ni-rich transition metal oxide is treated as the most promising alternative cathode due to their high-capacity and flexible composition.However,the severe lattice strain and slow Li-ion migration kinetics severely restrict their practical application.Herein,a novelty strategy induced pinning effect and defect structure in layered Ni-rich transition metal oxide cathodes is proposed via a facile cation(iron ion)/anion(polyanion)co-doping method.Subsequently,the effects of pinning effect and defect structure on element valence state,crystal structure,morphology,lattice strain,and electrochemical performance during lithiation/delithiation are systematically explored.The detailed characterizations(soft X-ray absorption spectroscopy(sXAS),in-situ X-ray diffraction(XRD),etc.)and density functional theory(DFT)calculation demonstrate that the pinning effects built-in LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)materials by the dual-site occupation of iron ions on lithium and transition metal sites effectively alleviate the abrupt lattice strain caused by an unfavorable phase transition and the subsequent induction of defect structures in the Li layer can greatly reduce the lithium-ion diffusion barrier.Therefore,the modified LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)exhibits a high-capacity of 206.5 mAh g^(-1)and remarkably enhanced capacity retention of 93.9%after 100 cycles,far superior to~14.1%of the pristine cathodes.Besides,an excellent discharge capacity of 180.1 mAh g^(-1)at 10 C rate is maintained,illustrating its remarkable rate capability.This work reports a pinning effect and defect engineering method to suppress the lattice strain and alleviate lithium-ion kinetic barriers in the Ni-rich layered cathodes,providing a roadmap for understanding the fundamental mechanism of an intrinsic activity modulation and structural design of layered cathode materials.展开更多
The EPR 9 factors for cubic, tetragonal and orthorhombic Fe^＋ centers in alkali halides MX （M= Li, Na; X = F, CI） are calculated from second-order perturbation formulas of g factors based on cluster approach for 3...The EPR 9 factors for cubic, tetragonal and orthorhombic Fe^＋ centers in alkali halides MX （M= Li, Na; X = F, CI） are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d^7 ions in three symmetries. From calculations, the g factors of these Fe^＋ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe^＋ centers are estimated. The results are discussed.展开更多
Pyrochlore oxide(Y_(2)Ru_(2)O_(7))has been identified as a promising catalyst for the oxygen evolution reaction(OER)in advanced green energy strategies.However,its electrochemical inertness necessitates the exploratio...Pyrochlore oxide(Y_(2)Ru_(2)O_(7))has been identified as a promising catalyst for the oxygen evolution reaction(OER)in advanced green energy strategies.However,its electrochemical inertness necessitates the exploration of an effective strategy to facilitate electronic modulation.This study proposes a surface modification approach involving the integration of defective NiFe(D-NiFe)nanoparticles onto a Y_(2)Ru_(2)O_(7)(YRO)support(YRO@D-NiFeP/Ru)using a Prussian blue analog(PBA).Numerous cyanide(CN)vacancies are generated through the oxidation treatment of the NiFe PBA grown on the YRO support,yielding a defective PBA precursor(YRO@D-PBA).Subsequent annealing facilitates the transformation to the D-NiFe nanoparticles on the YRO support(YRO@D-NiFeP/Ru),which augments the exposure of Ni3+active sites beneficial for the OER.Moreover,the reduction of Ru cations from YRO results in the exsolution of Ru nanoparticles,which promotes synergistic charge transfer from the nanoparticles to the interior of Y_(2)Ru_(2)O_(7).Consequently,YRO@D-NiFeP/Ru exhibits a remarkable voltage of 1.49 V at 10 mA·cm^(−2) and the lowest Tafel slope of 42.4 mV·dec^(−1).In addition,a Zn–air battery constructed with YRO@D-NiFeP/Ru exhibits an outstanding power density of 136.2 mW·cm^(−2) and high charge–discharge stability,confirming the applicability of YRO@D-NiFeP/Ru in metal-air batteries.展开更多
Design of a miniaturized lumped-element bandpass filter in multilayer liquid crystal polymer technology is proposed.Fractional bandwidth of the bandpass filter is 20%,operating at a center frequency of 500 MHz.In orde...Design of a miniaturized lumped-element bandpass filter in multilayer liquid crystal polymer technology is proposed.Fractional bandwidth of the bandpass filter is 20%,operating at a center frequency of 500 MHz.In order to further reduce the size and improve the performance of the proposed filter,defected ground structure(DGS)has been implemented in the filter.Based on this structure,the volume of the inductor is reduced by 60%eficiently compared with the inductor without DGS,and the Q-factor is increased up to 257%compared with the traditional multilayer spiral inductor.The measured results indicate that the designed filter has a very sharp stopband,an insertion loss of 2.3dB,and a return loss of 18.6dB in the passband.The whole volume of the fabricated filter is 0.032入_(g)×0.05入_(g)×0.00075入_(g),where Ag is the guided wavelength of the center frequency.The proposed filter is easily integrated into radio-frequency/microwave circuitry at a low manufacturing cost,especially wireless communication.展开更多
A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed t...A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed to enhance the beam scanning rate,while circular polarization is achieved by etchingπ-shaped slots on the top plane.To suppress the open stopband at broadside,offset circular DGSs are periodically etched on the ground plane.Their impact on the reflection coefficient and axial ratio is then analyzed through a parametric study.A prototype of the antenna is simulated,fabricated,and measured.Both simulated and measured results indicate a scanning rate of approximately 8.6,with continuous beam scanning from-41°to 59°across the 11.3-12.7 GHz operating band.The antenna maintains an axial ratio below 3 dB within the 11.5-12.3 GHz range.This design shows promise for use in wireless communication systems,particularly in environments with increasingly limited spectrum resources.展开更多
Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,an...Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.展开更多
In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2...In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2:1)displayed excellent photocatalytic CO_(2)reduction activity and high CO selectivity(12,412.23μmol g^(−1)h^(−1))under visible light irradiation(λ≥420 nm),which is 5 times that of NiFe-MOF.Notably,the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups,accelerating charge transfer and promoting space charge separation,as supported by the photo-electrochemical properties.To better understand the CO_(2)adsorption mechanism,density functional theory calculations were performed,which revealed that the Niov site has more negative adsorption energy compared with the Feov site.This study provides a simple strategy to establish efficient photocatalysts for CO_(2)reduction through the modification of organic ligands.展开更多
Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distor...Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired.In this paper,a compact Ultra-Wideband(UWB)V-shaped monopole antenna is presented.UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape.The proposed V-shaped is designed by incorporating a rectangle,and an inverted isosceles triangle using FR4 substrate.The size of the antenna is 25 mm×26 mm×1.6 mm.The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial,Scientific,and Medical(ISM),Worldwide Interoperability for Microwave Access(WiMAX),(IEEE 802.11/HIPERLAN band,5G sub 6 GHz)which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission(FCC)with a maximum gain of 3.83 dB.The antenna is designed in Ansys HFSS.Results for key performance parameters of the antenna are presented.The measured results are in good agreement with the simulated results.Due to flat gain,uniform group delay,omni directional radiation pattern characteristics and well-matched impedance,the proposed antenna is suitable for WiMAX,ISM and heterogeneous wireless systems.展开更多
In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna...In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit cell.However,the orientation which gives low-frequency resonance is considered here.The unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing side.This modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground plane.Specific parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the bandwidth.Finally,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance bandwidth.The proposed antenna is fabricated and measured.Experimental results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is realized.In addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.展开更多
The filter characteristic of defected ground structure (DGS) is analyzed and the equivalent circuit of C-shaped DGS is extracted. The characteristics of non-periodic and periodic DGS with different dimensions are comp...The filter characteristic of defected ground structure (DGS) is analyzed and the equivalent circuit of C-shaped DGS is extracted. The characteristics of non-periodic and periodic DGS with different dimensions are compared. Then the DGS is simulated and optimized with software, and the circuit board is manufactured and measured.The non-periodic structure is simple in structure and small in size and ripple compared with the periodic structure.Though the stop band of the non-periodic structure is narrow, it can meet the requirement of application. The C-shaped structure with two stop bands can select frequency in a special band.展开更多
A novel defected ground structure （DGS） for the microstrip line is proposed in this paper. The DGS lattice has more defect parameters so that it can provide better performance than the conventional dumbbell-shaped D...A novel defected ground structure （DGS） for the microstrip line is proposed in this paper. The DGS lattice has more defect parameters so that it can provide better performance than the conventional dumbbell-shaped DGS. Selectivity is improved by 97.2% with a sharpness factor of 24.6%. The method is applied to the design of a low-pass filter to confirm validity of the proposed DGS.展开更多
In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Elect...In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Electromagnetic Radiation Structures(ERS)is composed of multiple radiating elements.These MIMO antennas are designed and analyzed with and without DGS.The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size,which is 60×40×1 mm.The high directivity and divergence characteristics are attained by introducing the microstripfed lines perpendicular to each other.And the projected MIMO antenna structures are compared with others by using parameters like Return Loss(RL),Voltage Standing Wave Ratio(VSWR),Radiation Pattern(RP),radiation efficiency,and directivity.The same MIMO set-up is redesigned with DGS,and the resultant parameters are compared.Finally,the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL,VSWR,RP,radiation efficiency,and directivity.This projected antenna displays an omnidirectional RP with moderate gain,which is highly recommended for human healthcare applications.By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3,4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications.The proposed design covers numerous well-known wireless standards,along with dual-function DGS slots,and it can be easily integrated into Wireless Body Area Networks(WBAN)in medical applications.This WBAN links the autonomous nodes that may be situated either in the clothes,on-body or beneath the skin of a person.This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.展开更多
Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni（75）AlxV（25-x） alloys are in...Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni（75）AlxV（25-x） alloys are investigated using a microscopic phase field model to illuminate relations between anti-structured defects and composition,precipitate order,precipitate type,and phase stability.The Ni（75）AlxV（25-x） alloys undergo single Ni3V（stage Ⅰ）,dual Ni3Al and Ni3V（stage Ⅱ with Ni3V prior;and stage Ⅲ with Ni3Al prior）,and single Ni3Al（stage Ⅳ） with enhanced aluminum level.For Ni3V phase,anti-structured defects（V（Ni1）,Niy,except V（Ni2）） and substitution defects（Al（Ni1）,Al（Ni2）,Alv） exhibit a positive correlation to aluminum in stage I,the positive trend becomes to negative correlation or smooth during stage Ⅱ.For Ni3 Al phase,anti-structured defects（Al（Ni）,Ni（Al）） and substitution defects（V（Ni）,V（Al）） have a positive correlation to aluminum in stage Ⅱ,but Ni（Al） goes down since stage Ⅲ and lasts to stage Ⅳ.V（Ni） and V（Al） fluctuate when Ni3Al precipitates prior,but go down drastically in stageⅣ.Precipitate type conversion of single Ni3V/dual（Ni3V＋Ni3Al） affects Ni3V defects,while dual（Ni3V＋Ni3Al）/single Ni3 Al has little effect on Ni3Al defects.Precipitate order swap occurred in the dual phase region affects on Ni3Al defects but not on Ni3V.展开更多
Single atom catalysts(SACs) possessing regulated electronic structure, high atom utilization, and superior catalytic efficiency have been studied in almost all fields in recent years. Carbon-based supporting SACs are ...Single atom catalysts(SACs) possessing regulated electronic structure, high atom utilization, and superior catalytic efficiency have been studied in almost all fields in recent years. Carbon-based supporting SACs are becoming popular materials because of their low cost, high electron conductivity, and controllable surface property. At the stage of catalysts preparation, the rational design of active sites is necessary for the substantial improvement of activity of catalysts. To date, the reported design strategies are mainly about synthesis mechanism and synthetic method. The level of understanding of design strategies of carbon-based single atom catalysts is requiring deep to be paved. The design strategies about manufacturing defects and coordination modulation of catalysts are presented. The design strategies are easy to carry out in the process of drawing up preparation routes. The components of carbon-based SACs can be divided into two parts: active site and carbon skeleton. In this review, the manufacture of defects and coordination modulation of two parts are introduced, respectively. The structure features and design strategies from the active sites and carbon skeletons to the overall catalysts are deeply discussed.Then, the structural design of different nano-carbon SACs is introduced systematically. The characterization of active site and carbon skeleton and the detailed mechanism of reaction process are summarized and analyzed. Next, the applications in the field of electrocatalysis for oxygen conversion and hydrogen conversion are illustrated. The relationships between the superior performance and the structure of active sites or carbon skeletons are discussed. Finally, the conclusion of this review and prospects on the abundant space for further promotion in broader fields are depicted. This review highlights the design and preparation thoughts from the parts to the whole. The detailed and systematic discussion will provide useful guidance for design of SACs for readers.展开更多
基金supported by the National Natural Sci-ence Foundation of China(No.22174135,No.21790352)the National Key R&D Program of China(No.2021YFA1500500,No.2016YFA0200600)+4 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies(No.AHY090100)CAS Project for Young Scientists in Basic Research(No.YSBR-054)Innovation Program for Quantum Science and Technology(No.2021ZD0303301)the Fundamental Research Funds for the Central Universities.
文摘Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.
基金Project (50925521) supported by the National Natural Science Fund for Distinguished Young Scholars of China
文摘Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.
基金a joint National Natural Science Foundation of China-Deutsche Forschungsgemeinschaft(NSFC-DFG) project(NSFC grant 51861135313,DFG JA466/39-1)supported by National Natural Science Foundation of China(21706199)International Science & Technology Cooperation Program of China(2015DFE52870)Jilin Province Science and Technology Development Plan(20180101208JC)。
文摘Three-dimensional(3 D) hybrid of nanocarbons is a very promising way to the high-performance design of electrocatalysis materials.However,sp^(3)-like defect structure,a combination of high strength and conduction of graphene and carbon nanotubes(CNTs) is rarely reported.Herein,3 D neural-like hybrids of graphene(from reduced graphene oxide) and carbon nanotubes(CNTs) have been integrated via sp^(3)-like defect structure by a hydrothermal approach.The sp^(3)-like defect structure endows 3 D nanocarbon hybrids with an enhanced carrier transfer,high structural stability,and electrocatalytic durability.The neural-like structure is shown to demonstrate a cascade effect of charges and significant performances regarding bio-electrocatalysis and lithium-sulfur energy storage.The concept and mechanism of "sp^(3)-like defect structure" are proposed at an atomic/nanoscale to clarify the generation of rational structure as well as the cascade electron transfer.
基金supported by the National Natural Science Foundation of China (50672100)the Provincial Education Department of Jiangxi Province ([2006]313)
文摘As a mixed conductor,LaSr3Fe3O10-δ with triple layer perovskite intergrowth structure can be used as an oxygen separation membrane material and cathode material in solid oxide fuell cells.LaSr3Fe3O10-δ was synthesized via citrate acid route.Iodine titration method was used to determine the average valence of transition metal Fe and oxygen nonstoichiometry δ.Conductivities of LaSr3Fe3O10-δ were measured in the oxygen partial pressure range from 10-2×105 to 1×105 Pa,by Ac four probe method.Seebeck coefficient...
文摘The dielectric properties of ceramics with composition of (Sr 1-x Bi x )TiO 3+x/2 (where x =0.05～0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr 1-x Bi x )TiO 3+x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi 2O 3. The relative permittivity of the solid solutions is high, and the dissipation factor is low. The positron annihilation technique(PAT) was adopted to study the defect structure. An explanation of the dielectric properties of Bi-doped SrTiO 3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism.
文摘A set of potential parameters for modeling zircon was obtained by atomistic simulation techniques and a reasonable structural model of zircon was established by fitting some important properties of zircon.Based on the equilibrium configuration of zircon, authors calculated the formation energies of basic point defects and intrinsic disorders. The heats of solution of substituting Pu for Zr showed that there was an immiscible gap at the composition of (Pu75%-Zr25%, in mole fraction), which suggests that the amount of Pu substituting for Zr in zircon be≤50%.
基金financially supported by the Science and Technology of Guangxi Zhuang Autonomous Region(the Guangxi special Fund for Scientific Center and Talent Resources:AD18281073,Chongke 2018AD15002 and FA2020011)。
文摘Layered Ni-rich transition metal oxide is treated as the most promising alternative cathode due to their high-capacity and flexible composition.However,the severe lattice strain and slow Li-ion migration kinetics severely restrict their practical application.Herein,a novelty strategy induced pinning effect and defect structure in layered Ni-rich transition metal oxide cathodes is proposed via a facile cation(iron ion)/anion(polyanion)co-doping method.Subsequently,the effects of pinning effect and defect structure on element valence state,crystal structure,morphology,lattice strain,and electrochemical performance during lithiation/delithiation are systematically explored.The detailed characterizations(soft X-ray absorption spectroscopy(sXAS),in-situ X-ray diffraction(XRD),etc.)and density functional theory(DFT)calculation demonstrate that the pinning effects built-in LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)materials by the dual-site occupation of iron ions on lithium and transition metal sites effectively alleviate the abrupt lattice strain caused by an unfavorable phase transition and the subsequent induction of defect structures in the Li layer can greatly reduce the lithium-ion diffusion barrier.Therefore,the modified LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)exhibits a high-capacity of 206.5 mAh g^(-1)and remarkably enhanced capacity retention of 93.9%after 100 cycles,far superior to~14.1%of the pristine cathodes.Besides,an excellent discharge capacity of 180.1 mAh g^(-1)at 10 C rate is maintained,illustrating its remarkable rate capability.This work reports a pinning effect and defect engineering method to suppress the lattice strain and alleviate lithium-ion kinetic barriers in the Ni-rich layered cathodes,providing a roadmap for understanding the fundamental mechanism of an intrinsic activity modulation and structural design of layered cathode materials.
基金The project supported by National Natural Science Foundation of China under Grant No. 10274054
文摘The EPR 9 factors for cubic, tetragonal and orthorhombic Fe^＋ centers in alkali halides MX （M= Li, Na; X = F, CI） are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d^7 ions in three symmetries. From calculations, the g factors of these Fe^＋ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe^＋ centers are estimated. The results are discussed.
基金supported by Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(No.RS-2024-00398346,ESS BigData-Based O&M and Asset Management Technical Manpower Training)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00350658).
文摘Pyrochlore oxide(Y_(2)Ru_(2)O_(7))has been identified as a promising catalyst for the oxygen evolution reaction(OER)in advanced green energy strategies.However,its electrochemical inertness necessitates the exploration of an effective strategy to facilitate electronic modulation.This study proposes a surface modification approach involving the integration of defective NiFe(D-NiFe)nanoparticles onto a Y_(2)Ru_(2)O_(7)(YRO)support(YRO@D-NiFeP/Ru)using a Prussian blue analog(PBA).Numerous cyanide(CN)vacancies are generated through the oxidation treatment of the NiFe PBA grown on the YRO support,yielding a defective PBA precursor(YRO@D-PBA).Subsequent annealing facilitates the transformation to the D-NiFe nanoparticles on the YRO support(YRO@D-NiFeP/Ru),which augments the exposure of Ni3+active sites beneficial for the OER.Moreover,the reduction of Ru cations from YRO results in the exsolution of Ru nanoparticles,which promotes synergistic charge transfer from the nanoparticles to the interior of Y_(2)Ru_(2)O_(7).Consequently,YRO@D-NiFeP/Ru exhibits a remarkable voltage of 1.49 V at 10 mA·cm^(−2) and the lowest Tafel slope of 42.4 mV·dec^(−1).In addition,a Zn–air battery constructed with YRO@D-NiFeP/Ru exhibits an outstanding power density of 136.2 mW·cm^(−2) and high charge–discharge stability,confirming the applicability of YRO@D-NiFeP/Ru in metal-air batteries.
基金the Shaanxi Provincial Key Research and Development Program(No.2020GY-040)。
文摘Design of a miniaturized lumped-element bandpass filter in multilayer liquid crystal polymer technology is proposed.Fractional bandwidth of the bandpass filter is 20%,operating at a center frequency of 500 MHz.In order to further reduce the size and improve the performance of the proposed filter,defected ground structure(DGS)has been implemented in the filter.Based on this structure,the volume of the inductor is reduced by 60%eficiently compared with the inductor without DGS,and the Q-factor is increased up to 257%compared with the traditional multilayer spiral inductor.The measured results indicate that the designed filter has a very sharp stopband,an insertion loss of 2.3dB,and a return loss of 18.6dB in the passband.The whole volume of the fabricated filter is 0.032入_(g)×0.05入_(g)×0.00075入_(g),where Ag is the guided wavelength of the center frequency.The proposed filter is easily integrated into radio-frequency/microwave circuitry at a low manufacturing cost,especially wireless communication.
文摘A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed to enhance the beam scanning rate,while circular polarization is achieved by etchingπ-shaped slots on the top plane.To suppress the open stopband at broadside,offset circular DGSs are periodically etched on the ground plane.Their impact on the reflection coefficient and axial ratio is then analyzed through a parametric study.A prototype of the antenna is simulated,fabricated,and measured.Both simulated and measured results indicate a scanning rate of approximately 8.6,with continuous beam scanning from-41°to 59°across the 11.3-12.7 GHz operating band.The antenna maintains an axial ratio below 3 dB within the 11.5-12.3 GHz range.This design shows promise for use in wireless communication systems,particularly in environments with increasingly limited spectrum resources.
文摘Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.
基金the National Natural Science Foundation of China(Nos.51278001,U22A20401)Anhui Province Major Science and Technology Projects(No.202003a0702014)+1 种基金Natural Science Foundation of Anhui Province(No.2018085QD172)Natural Science Key Project of Education Department of Anhui Province(No.KJ2020A0017)for supporting this work.We thank Letpub(www.letpub.com.cn)for its linguistic assistance during the preparation of this manuscript.Thanks to the University of Science and Technology of China for providing MATERIAL STUDIO software copyright support.
文摘In this study,a Ni-Fe metal-organic framework modified by-NH_(2)and-SH was synthesized using a sim-ple hydrothermal process for enhancing photocatalytic CO_(2)reduction.As expected,the N2S-NiFe(NH_(2)-BDC/H_(4)DSBDC,2:1)displayed excellent photocatalytic CO_(2)reduction activity and high CO selectivity(12,412.23μmol g^(−1)h^(−1))under visible light irradiation(λ≥420 nm),which is 5 times that of NiFe-MOF.Notably,the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups,accelerating charge transfer and promoting space charge separation,as supported by the photo-electrochemical properties.To better understand the CO_(2)adsorption mechanism,density functional theory calculations were performed,which revealed that the Niov site has more negative adsorption energy compared with the Feov site.This study provides a simple strategy to establish efficient photocatalysts for CO_(2)reduction through the modification of organic ligands.
基金This work was supported by the Research Program through the National Research Foundation of Korea,NRF-2019R1A2C1005920,S.K.
文摘Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired.In this paper,a compact Ultra-Wideband(UWB)V-shaped monopole antenna is presented.UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape.The proposed V-shaped is designed by incorporating a rectangle,and an inverted isosceles triangle using FR4 substrate.The size of the antenna is 25 mm×26 mm×1.6 mm.The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial,Scientific,and Medical(ISM),Worldwide Interoperability for Microwave Access(WiMAX),(IEEE 802.11/HIPERLAN band,5G sub 6 GHz)which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission(FCC)with a maximum gain of 3.83 dB.The antenna is designed in Ansys HFSS.Results for key performance parameters of the antenna are presented.The measured results are in good agreement with the simulated results.Due to flat gain,uniform group delay,omni directional radiation pattern characteristics and well-matched impedance,the proposed antenna is suitable for WiMAX,ISM and heterogeneous wireless systems.
文摘In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit cell.However,the orientation which gives low-frequency resonance is considered here.The unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing side.This modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground plane.Specific parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the bandwidth.Finally,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance bandwidth.The proposed antenna is fabricated and measured.Experimental results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is realized.In addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.
基金Supported by Natural Science Foundation of China(No.60371029).
文摘The filter characteristic of defected ground structure (DGS) is analyzed and the equivalent circuit of C-shaped DGS is extracted. The characteristics of non-periodic and periodic DGS with different dimensions are compared. Then the DGS is simulated and optimized with software, and the circuit board is manufactured and measured.The non-periodic structure is simple in structure and small in size and ripple compared with the periodic structure.Though the stop band of the non-periodic structure is narrow, it can meet the requirement of application. The C-shaped structure with two stop bands can select frequency in a special band.
基金Project supported by the Shanghai Leading Academic Discipline Project (Grant No.T0102)
文摘A novel defected ground structure （DGS） for the microstrip line is proposed in this paper. The DGS lattice has more defect parameters so that it can provide better performance than the conventional dumbbell-shaped DGS. Selectivity is improved by 97.2% with a sharpness factor of 24.6%. The method is applied to the design of a low-pass filter to confirm validity of the proposed DGS.
文摘In this paper,the investigation of a novel compact 2×2,2×1,and 1×1 Ultra-Wide Band(UWB)based Multiple-Input Multiple-Output(MIMO)antenna with Defected Ground Structure(DGS)is employed.The proposed Electromagnetic Radiation Structures(ERS)is composed of multiple radiating elements.These MIMO antennas are designed and analyzed with and without DGS.The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size,which is 60×40×1 mm.The high directivity and divergence characteristics are attained by introducing the microstripfed lines perpendicular to each other.And the projected MIMO antenna structures are compared with others by using parameters like Return Loss(RL),Voltage Standing Wave Ratio(VSWR),Radiation Pattern(RP),radiation efficiency,and directivity.The same MIMO set-up is redesigned with DGS,and the resultant parameters are compared.Finally,the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL,VSWR,RP,radiation efficiency,and directivity.This projected antenna displays an omnidirectional RP with moderate gain,which is highly recommended for human healthcare applications.By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3,4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications.The proposed design covers numerous well-known wireless standards,along with dual-function DGS slots,and it can be easily integrated into Wireless Body Area Networks(WBAN)in medical applications.This WBAN links the autonomous nodes that may be situated either in the clothes,on-body or beneath the skin of a person.This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.
基金Project supported by the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2016JQ5014)the Fundamental Research Funds for the Central Universities,China(Grant No.3102014JCQ01024)+2 种基金the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China(Grant No.114-QP-2014)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20136102120021)the National Natural Science Foundation of China(Grant Nos.51474716 and 51475378)
文摘Anti-structured defects bridge atom migration among heterogeneous sublattices facilitating diffusion but could also result in the collapse of ordered structure.Component distribution Ni（75）AlxV（25-x） alloys are investigated using a microscopic phase field model to illuminate relations between anti-structured defects and composition,precipitate order,precipitate type,and phase stability.The Ni（75）AlxV（25-x） alloys undergo single Ni3V（stage Ⅰ）,dual Ni3Al and Ni3V（stage Ⅱ with Ni3V prior;and stage Ⅲ with Ni3Al prior）,and single Ni3Al（stage Ⅳ） with enhanced aluminum level.For Ni3V phase,anti-structured defects（V（Ni1）,Niy,except V（Ni2）） and substitution defects（Al（Ni1）,Al（Ni2）,Alv） exhibit a positive correlation to aluminum in stage I,the positive trend becomes to negative correlation or smooth during stage Ⅱ.For Ni3 Al phase,anti-structured defects（Al（Ni）,Ni（Al）） and substitution defects（V（Ni）,V（Al）） have a positive correlation to aluminum in stage Ⅱ,but Ni（Al） goes down since stage Ⅲ and lasts to stage Ⅳ.V（Ni） and V（Al） fluctuate when Ni3Al precipitates prior,but go down drastically in stageⅣ.Precipitate type conversion of single Ni3V/dual（Ni3V＋Ni3Al） affects Ni3V defects,while dual（Ni3V＋Ni3Al）/single Ni3 Al has little effect on Ni3Al defects.Precipitate order swap occurred in the dual phase region affects on Ni3Al defects but not on Ni3V.
基金funded by the National Natural Science Foundation of China (Nos. 22279118, 31901272, 21401168, U1204203)National Science Fund for Distinguished Young of China (No. 22225202)+1 种基金Young Top Talent Program of Zhongyuan-YingcaiJihua (No. 30602674)Top-Notch Talent Program of Henan Agricultural University (No. 30501034)。
文摘Single atom catalysts(SACs) possessing regulated electronic structure, high atom utilization, and superior catalytic efficiency have been studied in almost all fields in recent years. Carbon-based supporting SACs are becoming popular materials because of their low cost, high electron conductivity, and controllable surface property. At the stage of catalysts preparation, the rational design of active sites is necessary for the substantial improvement of activity of catalysts. To date, the reported design strategies are mainly about synthesis mechanism and synthetic method. The level of understanding of design strategies of carbon-based single atom catalysts is requiring deep to be paved. The design strategies about manufacturing defects and coordination modulation of catalysts are presented. The design strategies are easy to carry out in the process of drawing up preparation routes. The components of carbon-based SACs can be divided into two parts: active site and carbon skeleton. In this review, the manufacture of defects and coordination modulation of two parts are introduced, respectively. The structure features and design strategies from the active sites and carbon skeletons to the overall catalysts are deeply discussed.Then, the structural design of different nano-carbon SACs is introduced systematically. The characterization of active site and carbon skeleton and the detailed mechanism of reaction process are summarized and analyzed. Next, the applications in the field of electrocatalysis for oxygen conversion and hydrogen conversion are illustrated. The relationships between the superior performance and the structure of active sites or carbon skeletons are discussed. Finally, the conclusion of this review and prospects on the abundant space for further promotion in broader fields are depicted. This review highlights the design and preparation thoughts from the parts to the whole. The detailed and systematic discussion will provide useful guidance for design of SACs for readers.
